From 4a240f6ce7aa275f0c8fb4fb0bab18ef29e8cb5f Mon Sep 17 00:00:00 2001
From: Alexander Motin <mav@FreeBSD.org>
Date: Sun, 29 Dec 2013 03:43:25 +0000
Subject: [PATCH] In addition to r259632 completely block receive upcalls if we
 have more data than we need.  This reduces lock pressure from xprt_active()
 side.

---
 sys/rpc/svc_vc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/sys/rpc/svc_vc.c b/sys/rpc/svc_vc.c
index 988b487eba55..f9ff0e6f598e 100644
--- a/sys/rpc/svc_vc.c
+++ b/sys/rpc/svc_vc.c
@@ -619,7 +619,15 @@ svc_vc_process_pending(SVCXPRT *xprt)
 		}
 	}
 
-	so->so_rcv.sb_lowat = imax(1, imin(cd->resid, so->so_rcv.sb_hiwat / 2));
+	/*
+	 * Block receive upcalls if we have more data pending,
+	 * otherwise report our need.
+	 */
+	if (cd->mpending)
+		so->so_rcv.sb_lowat = INT_MAX;
+	else
+		so->so_rcv.sb_lowat =
+		    imax(1, imin(cd->resid, so->so_rcv.sb_hiwat / 2));
 	return (TRUE);
 }